class Launcher

Acquire the launcher service. This can be done just once and then reused

across all tests.

Launch a test process as if it were userboot, inside the test job. (It

fails quickly if the job is invalid, so TestJob::Get() can be passed in

unchecked.) This sends an initial message with essential handles about

the process itself, which is handled by the custom startup code in the

userboot library. The log fd is a pipe whose underlying zx::socket is

sent in place of the zx::debuglog sent in the kernel's initial message

(the libc startup code handles either one). The handles are whatever it

expects from the kernel in the second message, which the userboot program

will read via TakeBootstrapChannel() from

<lib

/userboot/startup.h>.

The handles in each message are always shuffled pseudo-randomly to test

that the userboot program is not sensitive to their order, as there is no

guarantee what order the kernel will use. The shuffle is based on gtest

testing::UnitTest::random_seed() so it can be recreated via the logging

and machinery that gtest provides for its random permutation testing.